1. Field of the Invention
The invention relates to a nozzle for directing discrete streams of air along separated and parallel first and second paths, and is directed more particularly to such a nozzle for a device for heat welding two overlapping roof and/or waterproofing membranes to each other.
2. Description of the Prior Art
It is known to provide a device for heat welding two overlapping roof membranes to each other, and to provide such device with a nozzle for directing discrete streams of fluid along separated and parallel first and second weld paths. See, for example, U.S. Pat. No. 4,834,828, issued May 28, 1989, to Colin R. R. Murphy.
The Murphy patent relates to a machine for effecting continuous heat welds on either side of a fastener means, such as a row of fasteners, or an elongated bar. To effect the parallel welds simultaneously, the Murphy machine is provided with a nozzle which directs a stream of hot air to generally parallel paths on both sides of the fastener means. The upper overlapping membrane is heat sealed to the lower overlapped membrane along the overlap portion to seal the two membranes together on either side of the fastener means. The fastener means fastens the lower membrane to an uppermost hard surface of a roof, and is, in turn, covered by the upper membrane. To effect the two welds simultaneously, the nozzle is essentially a bifurcated nozzle which is moved by the machine between the two membranes, under an edge of the upper membrane.
The Murphy nozzle is provided with two outlets substantially side-by-side and in substantially the same plane, heightwise. The two outlets are separated by a bridge portion which connects the two outlets and channels hot air thereto. It has been found that the nozzle arrangement is not entirely satisfactory in that the closeness of the two welding locations causes one to adversely influence the other. It has been found that air flows vary in intensity and temperature due to nozzle design. Further, hot air from one nozzle outlet crosses over to the area impacted by the other nozzle outlet and causes bubbling or rippling of the upper membrane on the lower membrane. It has further been found that the two outlets, being in substantially the same plane, both tend to drag along the surface of the lower membrane and cause the nozzle bridge portion, i.e., the nozzle portion between the two outlets, to move along the fastener means with insufficient clearance. Still further, because the Murphy nozzle outlets are in the same vertical plane, and weld simultaneously, the membranes tend to move, causing wrinkles. When the fastener means comprises a row of discrete fasteners or elements, the nozzle bridge portion is bounced upwardly upon encountering a fastener or element, causing the nozzle outlets to rise momentarily, effecting a non-welding segment in both weld paths and potentially creating "fishmouths" in seams. The Murphy nozzle, when inserted into the membrane overlays, is locked into position and cannot accommodate irregularities in the substrate without diminishing seam quality.
There is thus a need for an improved nozzle of the type described above, but in which the welds are effected concurrently but at points removed from each other such that one weld contributes to another, rather than detracting from the other, and in which the welds are effected continuously and free from interruptions caused by collisions with the fastener means.